Mobile communications have changed the way people communicate and mobile phones have been transformed from a luxury item to an essential part of every day life. The use of mobile phones today is dictated by social situations, rather than hampered by location or technology. While voice connections fulfill the basic need to communicate, and wireless voice and data connections continue to filter even further into the fabric of every day life, various integrated mobile multimedia applications, utilizing wireless and/or wired networks, may be the next step in the mobile communication revolution.
Third generation (3G) cellular networks offering various high speed access technologies and mobile telephones that have been specifically designed to utilize these technologies, fulfill demands for integrated multimedia applications supporting TV and audio applications utilizing advanced compression standards, high-resolution gaming applications, musical interfaces, peripheral interface support, etc. The processing requirements are being increased as chip designers take advantage of compression and higher bandwidths to transmit more information. 3G wireless applications support bit rates from 384 kilobits (Kbits)/second to 2 megabits (Mbits)/second, allowing chip designers to provide wireless systems with multimedia capabilities, superior quality, reduced interference, and a wider coverage area.
As mobile multimedia services grow in popularity and usage, factors such as power consumption, cost efficient optimization of network capacity and quality of service (QoS) continue to be even more essential to cellular operators than it is today. These factors may be achieved with careful network planning and operation, improvements in transmission methods, and advances in receiver techniques and chip integration solutions. To this end, carriers need technologies that will allow them to increase downlink throughput for the mobile multimedia applications support and, in turn, offer advanced QoS capabilities and speeds for consumers of mobile multimedia application services. Currently, mobile multimedia processors may not fully utilize system-on-a-chip (SoC) integration for advanced total system solution for today's mobile handsets. For example, conventional mobile processors may utilize a plurality of hardware accelerators to enable a variety of multimedia applications, which significantly increases power consumption, implementation complexity, mobile processor real estate, and ultimately terminal size.
Some mobile communications technologies, for example the global system for mobile communications (GSM), general packet radio service (GPRS), and enhanced data rates for GSM evolution (EDGE) may utilize polar modulation. Polar modulation may comprise converting a signal from a representation that utilizes in-phase (I), and quadrature phase (Q) components, to a corresponding representation that utilizes magnitude (ρ) and phase (φ) components. Quantization noise may be introduced as a result of the conversion from the I and Q signal representation to the ρ and φ signal representation. Consequently, at least a portion of the components in the ρ and φ signal representation may be filtered.
There are numerous existing integrated circuit (IC) designs for direct modulation and/or polar modulation transmitters that are based on fractional-N phase locked loop (PLL) and/or sigma delta modulation techniques. Many of these IC designs comprise mixed analog and digital signals for which CMOS technology may be a semiconductor fabrication technology of choice for maintaining low power consumption and manufacturing cost. However, variations in component parameter values introduced during IC manufacturing, and temperature variations introduced during circuit operation may require that analog component values be adjustable, or tunable, to control component behavior. A particular area of concern is a low pass filtering characteristic that is typical in many PLL designs. This may pose a particular problem when a cutoff frequency of the low pass filter is within the range of frequencies utilized by a direct modulation and/or polar modulation transmitter for transmitting signals. As a result, an input signal that is being modulated by the direct modulation or polar modulation transmitter may become distorted. In turn, the modulation output signal may become distorted. The result is that the transmitted signal, when received at a receiver device, may not present a faithful reproduction of the original input signal that was submitted for transmission.
In some existing direct modulation and/or polar modulation transmitters, analog component values in PLL circuitry may be tunable by utilizing analog control circuitry. However, one limitation of the use of analog control circuitry to control analog PLL circuitry may involve mismatches between components in the analog PLL circuitry and components in the analog control circuitry. A limitation associated with the use of such circuitry in polar modulation transmitters may involve the introduction of timing misalignment between a phase signal path, and an amplitude signal path utilized for the input signals to the polar modulation transmitter.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.